Sheet feed image scanning apparatus

ABSTRACT

A sheet feed image scanning apparatus comprises a sheet feeding unit mounted to an image scanning unit. The sheet feeding unit has a casing that comprises the mount of a sheet conveyor assembly to convey a document sheet along a conveyance path that passes over a scanning window. The sheet conveyor assembly comprises a motor-driven central conveyor roller and a plurality of idler rollers mounted in circumferential contact with the central conveyor roller. The document introduced in the sheet feeding unit engages between the central conveyor roller and the idler rollers to be conveyed over the scanning window, through which the scanning unit captures an image of the document sheet.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the priority benefit of Taiwan application serial no.91124656, filed on Oct. 24, 2002.

BACKGROUND OF INVENTION

[0002] 1. Field of the Invention

[0003] The invention relates generally to a sheet feed image scanning apparatus and, more particularly, to a sheet feeding unit implemented in the sheet feed image scanning apparatus that is dimensionally reduced.

[0004] 2. Description of the Related Art

[0005]FIG. 1 is a schematic view that illustrates a sheet feeding apparatus known in the prior art. The sheet feeding apparatus 110 of the prior art comprises a casing 112 in which are mounted three pairs of conveyor rollers, a sheet separating roller 118, a sheet separating plate 120, a sheet pickup roller 122 and a driving motor 124. The sheet pickup roller 122 engages a document sheet introduced in the sheet feeding apparatus 110. The sheet separating roller 118 is mounted in a manner such that its roller surface is adjacent to the sheet separating plate 120 to ensure that only a single document sheet 150 effectively engages through the pairs of conveyor rollers.

[0006] Each pair of conveyor rollers comprises a feeding roller 114 and an idler roller 116. The pairs of conveyor rollers are placed approximately around the driving motor 124 to pinch and convey the document sheet 150, the feeding rollers 114 being driven in rotation via the driving motor 124.

[0007] With the above construction, the sheet pickup roller 122 engages a document sheet 150 that is introduced in the casing 112, and forwards this document sheet 150 to the sheet separating roller/plate 118, 120. The sheet separating roller/plate 118, 120 separates one document sheet 150 if more than one document sheet has been fed, and forwards it to the conveyor rollers. The document sheet 150 then travels through the conveyor rollers until it exits the sheet feeding apparatus 110.

[0008] As illustrated in FIG. 1, the above construction usually requires the mount of the sheet separating roller/plate 118, 120 to be at a position above the first pair of conveyor rollers to obtain an effective engagement of the document sheet 150 there through. Furthermore, to enable an effective engagement and conveyance of the document sheet, the placement of the different pairs of conveyor rollers has to follow specific design rules. This results in a conveyance structure that is relatively complex and necessitates a larger space, which increases the height of the sheet feeding apparatus. Furthermore, the engagement of the document sheet between the pairs of conveyor rollers may be deficient if, for example, a front edge of the document sheet is folded, which causes paper jams.

SUMMARY OF INVENTION

[0009] An aspect of the invention is therefore to provide a sheet feeding unit that has a dimensionally reduced height.

[0010] Another aspect of the invention is to provide a sheet feeding unit that simplifies the structure design and reduces the fabrication cost.

[0011] Furthermore, another aspect of the invention is to provide a sheet feeding unit that is mounted in a sheet feed image scanning apparatus to convey a document sheet to be scanned.

[0012] To accomplish the above and other objectives, a sheet feeding unit of the invention comprises a casing in which are mounted a sheet pickup roller, a sheet separating roller, a sheet separating plate, a sheet conveyor assembly, and a driving motor. The casing includes a rear side and an opposite front side through which a document sheet is introduced in the sheet feeding unit and engages the sheet pickup roller. The sheet pickup roller forwards the document sheet to the sheet separating roller/plate. The sheet separating roller and the sheet separating plate are mounted facing each other with the roller surface of the sheet separating roller adjacent to the sheet separating plate. This assembly ensures that only a single document sheet, if more than one document sheet has been introduced, subsequently engages the sheet conveyor assembly. The sheet conveyor assembly comprises a central conveyor roller around which are mounted a plurality of idler rollers in circumferential contact with the central conveyor roller, the central conveyor roller being driven in rotation via the driving motor. After the sheet separating roller/plate, the document sheet engages between the central conveyor roller and the idler rollers by having a sheet surface in substantial contact with the roller surface of the central conveyor roller. By rotation of the central conveyor roller, the document sheet is conveyed along a conveyance path that terminates at a location of the casing where the scanned document sheet is externally retrieved.

[0013] According to a preferred embodiment, the driving motor, the central conveyor roller, the sheet separating roller/plate, and the sheet pickup roller are mounted within the casing successively along an axis that runs from the rear side to the front side.

[0014] According to a variant embodiment, the sheet conveyor assembly further comprises one or more belts that are wound around at least two idler rollers.

[0015] Implemented in a sheet feed image scanning apparatus, the above sheet feeding unit is assembled with an image scanning unit that comprises a scanning module to which is mounted a light source. The casing of the sheet feeding unit further defines a scanning window that is at a location facing the conveyance path of the document sheet. The light source projects an incident light through the scanning window onto the document sheet being conveyed by the central conveyor roller. A resulting image light passes through the scanning window and is captured by the scanning module, comprising an image sensor and an adequate assembly of reflecting mirrors and objective lens, to form an image of the document sheet.

[0016] It is to be understood that both the foregoing general description and the following detailed: description are exemplary, and are intended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF DRAWINGS

[0017] The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. In the drawings,

[0018]FIG. 1 is a schematic view illustrating a sheet feeding unit known in the prior art;

[0019]FIG. 2 is a schematic view illustrating a sheet feed image scanning apparatus according to an embodiment of the invention;

[0020]FIG. 3 is a schematic view illustrating a scanning module mounted in the sheet feed image scanning apparatus according to an embodiment of the invention; and

[0021]FIG. 4 is a schematic view illustrating a sheet feed image scanning apparatus according to a variant embodiment of the invention.

DETAILED DESCRIPTION

[0022] The following detailed description of the embodiments and examples of the present invention with reference to the accompanying drawings is only illustrative and not limiting. Furthermore, wherever possible in the description, the same reference symbols will refer to similar elements and parts unless otherwise illustrated in the drawings.

[0023] Referring to FIG. 2, a schematic view illustrates a sheet feed image scanning apparatus according to an embodiment of the invention. As illustrated, a sheet feed image scanning apparatus 200 of the invention comprises a sheet feeding unit 210 that is assembled with an image scanning unit 260. The sheet feeding unit 210 conveys a document sheet 250 to be scanned by the image scanning unit 260.

[0024] The construction of the sheet feeding unit 210 comprises a casing 212 in which are mounted a sheet pickup roller 222, a sheet separating roller 218, a sheet separating plate 220, and a sheet conveyor assembly driven by a driving motor 224 to convey the document sheet 250. According to a preferred embodiment of the invention, the sheet conveyor assembly comprises a central conveyor roller 214 and a plurality of idler rollers 216 a, 216 b, 216 c, 216 d mounted around the central conveyor roller 214. The casing 212 has a front side 230 through which a document sheet to be scanned is introduced in the sheet feeding unit 210, and an opposite rear side 232 in the proximity of which is placed the driving motor 224.

[0025] The sheet pickup roller 222 is mounted proximate to the front side 230 of the casing 212 to engage a document sheet to be scanned. After the sheet pickup roller 222, both sheet separating roller 218 and sheet separating plate 220 are mounted facing each other, with a roller surface of the sheet separating roller 218 adjacent to the sheet separating plate 220. The function of the sheet separating roller/plate 218, 220 is to ensure that only a single sheet of document 250, if more than one document sheet has been fed through the front side 230, engages through the sheet conveyor assembly. For this purpose, the coefficient of friction between the roller surface of the sheet separating roller 218 and a document sheet is preferably higher than that between two document sheets and higher than that between the sheet separating plate 220 and a document sheet in contact with it. Thereby, if more than one document sheet are fed, the sheet separating roller 218 will separate and forward one single document sheet 250 to the central conveyor roller 214.

[0026] The idler rollers 216 a, 216 b, 216 c, 216 d contact with the central conveyor roller 214 along its circumference to pinch and convey the document sheet 250 there between. The central conveyor roller 214 is driven in rotation via the driving motor 224 while the idler rollers 216 a, 216 b, 216 c, 216 d freely rotate.

[0027] To perform scanning, a document sheet 250 is inserted through the front side 230, engages through the sheet pickup roller 222, and passes through the sheet separating roller/plate 218, 220 to reach the central conveyor roller 214. The central conveyor roller 214 and the idler rollers 216 a˜216 d then convey the document sheet 250 along a direction that passes over a scanning window 213 and terminates over an area of the casing 212 where the scanned document sheet can be retrieved. As illustrated, the scanning window 213 may be formed through, for example, a lower wall of the casing 212, and the conveyance path of the document sheet includes a curved portion that substantially matches the circumference of the central conveyor roller 214 to pass over the scanning window 213.

[0028] According to a preferred configuration, the driving motor 224, the central conveyor roller 214, the sheet separating roller/plate 218, 220, and the sheet pickup roller 222 are mounted within the casing 212 successively along an axis that runs from the rear side 232 to the front side 230. By means of this lengthwise mount, the height of the sheet feeding unit 210 is substantially reduced. Furthermore, by using a single central conveyor roller assisted with idler rollers to convey the document sheet, the assembly structure is simplified. Via a substantially large contact surface area with the central conveyor roller 214, the document sheet 250 is further better engaged and conveyed, which enables an optimal scanning operation through the scanning window 213.

[0029] As illustrated in FIG. 2, the image scanning unit 260 comprises a casing 262, a transparent panel 264, and a scanning module 266. The casing 262 includes a hollow interior 263 where is received the scanning module 266, the hollow interior 263 having an external opening over which is mounted the transparent panel 264. The sheet feeding unit 210 is mounted to the image scanning unit 260 in such a manner that the scanning window 213 and the scanning module 266 are opposite to each other relative to the transparent panel 264.

[0030] Referring to FIG. 3, a schematic view illustrates the principal structure of a scanning module according to an embodiment of the invention. The scanning module 266 comprises a module casing 270, a lamp 272, an assembly of reflecting mirrors 274, an objective lens 276, an image sensor 278, and a circuit board 280. The lamp 272 is mounted to the module casing 270 by means of a support base 271 placed below the transparent panel 264. The assembly of reflecting mirrors 274 and the objective lens 276 are placed within the module casing 270, and the circuit board 280 is attached to one side of the module casing 270, the image sensor 278 being electrically connected on the circuit board 280. The image sensor 278 may be, for example, a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) image sensor. The module casing 270 further includes an opening 273 through which the image light from the document sheet 250 is captured.

[0031] The lamp 272 may be, for example, a cold cathode lamp that projects an incident light 275 through the transparent panel 264 and scanning window 213 onto the document sheet 250. A resulting image light 252 from the document sheet 250 then travels through the scanning window 213 and the transparent panel 264, penetrates the module casing 270 through an opening 273, and via the assembly of reflecting mirrors 274 is directed to the objective lens 276 to form an image on the image sensor 278. The sheet feed image scanning apparatus 200 therefore operates via progressively moving the document sheet 250 by means of the sheet feeding unit 210 while the image scanning unit 260 scans the image of the document sheet 250 through the scanning window 213.

[0032]FIG. 4 illustrates a variant embodiment of the sheet feeding unit 310. As illustrated, the sheet conveyor assembly in the casing 312 may additionally include a belt 328 that is wound around, for example, idler rollers 316 a, 316 b and is in contact with the roller surface of the central conveyor roller 314. After the sheet separating roller/plate 318, 320, the document sheet 350 to be scanned is conveyed by means of the central conveyor roller 314 successively through the belt 328 and idler rollers 316 c, 316 d. Via a larger contact surface area with the belt 328, the document sheet 350 is securely engaged through the sheet conveyor assembly, and folding of the document sheet, causing paper jams, is further prevented. The coefficient of friction between the belt surface and the document sheet 350 is preferably smaller than that between the roller surface of the central conveyor roller 314 and the document sheet 350 for it to be effectively conveyed by the central conveyor roller 314.

[0033] In a variant arrangement, the belt 328 may be wound around, for example, three idler rollers (not shown) and/or more belts may be mounted to secure the engagement of the document sheet. It will be therefore appreciated that the above sheet conveyor assembly may be modified according to different manners to achieve the same function of securely conveying the document sheet via the central conveyor roller.

[0034] As described above, the invention therefore includes at least the following advantages. By achieving a lengthwise mounting, the total height of the sheet feed image scanning apparatus is favorably reduced. Furthermore, via an enlarged contact surface area with the roller surface of the central conveyor roller, the document sheet more securely engages in the sheet conveyor assembly. The engagement and conveyance of the document sheet may also be further improved via the addition of belt elements in contact with the central conveyor roller to engage the document sheet.

[0035] It should be apparent to those skilled in the art that other structures that are obtained from various modifications and variations of different parts of the above-described structure of the invention would be possible without departing from the scope and spirit of the invention as illustrated herein. Therefore, the above description of embodiments and examples only illustrates specific ways of making and performing the invention that, consequently, should cover variations and modifications thereof, provided they fall within the inventive concepts as defined in the following claims. 

1. A sheet feeding unit suitable for being mounted in a sheet feed image scanning apparatus to convey a document sheet that is to be scanned, the sheet feeding unit comprising: a casing, having a rear side and a front side through which the document sheet is introduced in the sheet feeding unit; a sheet conveyor assembly, mounted in the casing and including a central conveyor roller that has a roller surface, the document sheet introduced in the sheet feeding unit engaging through the sheet conveyor assembly by having a sheet surface that is in contact with the roller surface of the central conveyor roller; and a driving motor, driving the central conveyor roller in rotation to convey the document sheet along a conveyance path.
 2. The sheet feeding unit of claim 1, wherein the conveyance path includes a curved portion that substantially matches with a circumference of the central conveyor roller.
 3. The sheet feeding unit of claim 1, wherein the sheet conveyor assembly further includes a plurality of idler rollers that contact with the central conveyor roller along a circumferential direction thereof to engage and convey the document sheet there between.
 4. The sheet feeding unit of claim 3, wherein the sheet conveyor assembly further includes a belt that is wound around at least two of the idler rollers and is in contact with the roller surface of the central conveyor roller to engage and convey the document sheet there between.
 5. The sheet feeding unit of claim 4, wherein the coefficient of friction between the roller surface of the central conveyor roller and the document sheet is greater than that between the belt and the document sheet.
 6. The sheet feeding unit of claim 1, further including a sheet pickup roller, a sheet separating roller and a sheet separating plate that are arranged with the central conveyor roller and the driving motor successively along an axis running from the front side to the rear side of the casing.
 7. The sheet feeding unit of claim 6, wherein the sheet pickup roller is mounted proximate to the front side to engage the document sheet, and the sheet separating plate and the sheet separating roller are mounted between the sheet pickup roller and the sheet conveyor assembly to ensure that a single document sheet engages through the sheet conveyor assembly.
 8. An image scanning apparatus, having a front side through which a document sheet to be scanned is introduced therein, the image scanning apparatus comprising: a sheet conveyor assembly, including a motor-driven central conveyor roller that has a roller surface, the introduced document sheet engaging through the sheet conveyor assembly by having a sheet surface in contact with the roller surface, the document sheet being thereby conveyed via a rotation of the central conveyor roller along a conveyance path that passes over a scanning window defined through an inner wall of the sheet feed image scanning apparatus; and an image scanning unit, mounted at a location that faces the conveyance path to capture an image of the document sheet through the scanning window.
 9. The image scanning apparatus of claim 8, wherein the conveyance path includes a curved portion that substantially matches with a circumference of the central conveyor roller.
 10. The image scanning apparatus of claim 8, wherein the sheet conveyor assembly further includes a plurality of idler rollers that contact with the central conveyor roller along a circumferential direction thereof to engage and convey the document sheet there between.
 11. The image scanning apparatus of claim 10, wherein the sheet conveyor assembly further includes a belt that is wound around at least two of the idler rollers and is in contact with the roller surface of the central conveyor roller to engage and convey the document sheet there between.
 12. The image scanning apparatus of claim 11, wherein the coefficient of friction between the roller surface of the central conveyor roller and the document sheet is greater than that between the belt and the document sheet.
 13. The image scanning apparatus of claim 8, further including a sheet pickup roller mounted proximate to the front side to engage the document sheet, and a sheet separating roller and a sheet separating plate that are mounted between the sheet pickup roller and the sheet conveyor assembly to ensure that a single document sheet engages through the sheet conveyor assembly.
 14. The image scanning apparatus of claim 8 wherein the image scanning unit comprises a source light and a scanning module, the source light emitting a light passing through the scanning window to strike the document sheet and produce an image light that is captured by the scanning module.
 15. The image scanning apparatus of claim 14, wherein the scanning module comprises an assembly of reflecting mirrors, an objective lens, and an image sensor.
 16. The image scanning apparatus of claim 15, wherein the image sensor includes a charge coupled device or a complementary metal oxide semiconductor image sensor. 